Multilayer hull for a small boat

ABSTRACT

This disclosure comprises a panel, shell, hull of a boat, or other formed shape which consists of outer and inner thin sheets of aluminum bonded together and made rigid by an internal layer of epoxy or other resinous cement.

Feb. 2, 1971` P. s. JUHNKE MULTILAYER HULL FOR A SMALL BOAT Filed Jan. 11, `mcsa United States Patent O U.S. Cl. 9-6 1 Claim ABSTRACT OF THE DISCLOSURE This disclosure comprises a panel, shell, hull of a boat, or other formed shape which consists of outer and inner thin sheets of aluminum bonded together and made rigid by an internal layer of epoxy or other resinous cement.

BACKGROUND OF THE INVENTION (1) Field of invention This invention relates in particular to small lightweight boats which can be inexpensively constructed from thin sheets of aluminum bonded together and rigidized by an internal layer of resinous cement. However such layerized sheets may 'be used in the construction of any forms where lightweight is essential.

(2) Description of the prior art SUMMARY OF THE INVENTION The essence of this invention is the use of thin outer and inner layers or skins of aluminum bonded by a layer of resinous cement. The sheets are thin enough to be easily formed in a press and are less than one-half the ordinary thickness used on aluminum hulls of small boats or canoes. A thickness as little as 0.010 inch have been found practical. However a thickness of 0.020 inch provides suicient ilexibility for easy forming and is also economical. The inner layer of sprayed-on self-curing epoxy is not used for effecting otation but solely to provide bonding strength and rigidity, Hence there is a saving in weight and cost of aluminum. The aluminum can be more easily formed. The hull thus formed has the advantageous resistance to tearing (known as tearing strength) of a solid sheet aluminum hull but in comparison is lighter in Weight and less expensive t manufacture.

In the event greater rigidity and/or stability is required ribs can be introduced with the forming of the aluminum skins. The internal voids created by such ribs are filled with the rigid adhesive. Also enlarged recesses may be formed and filled with enough volume of the cement to provide holding power for screws used to attach seat supports and the like.

BRIEF DESCRIPTION OF THE DRAWING In the drawing:

FIG. 1 is a perspective View of a hull of a boat formed with thin sheets of aluminum bonded together and made rigid by an internal layer of epoxy in accordance with the present invention;

FIG. 2. is an enlarged fragmentary section view taken on the meandering section line 2-2 of FIG. 1;

FIG. 3 is an exploded view of a male die or form, a

3,559,221 Patented Feb. 2 1971 ICC thin sheet of aluminum before forming and the outer shell of the hull of a boat which has been previously formed from a similar sheet and before the application of a layer of epoxy to the inner surface of such outer shell; and

FIG. 4 is a portion of a boat structure embodiment in which corrugated sheets are used for the inner and outer shells.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawing 'by reference numerals the hull of a small lightweight boat 10 (see FIG. l) of standard design is formed by an inner metal skin or shell 12 and an outer metal skin or shell 14 bonded together and made rigid by an internal layer of epoxy 16. Preferably these skins 12 and 14 are formed from a sheet of aluminum 18 (see FIG. 3) approximately 0.010 inch thick. The outer skin 14 is first formed from a sheet 18 by use of male die, not shown, but similar to the die 20 of FIG. 3. Then a layer of epoxy is applied to the inner surface of the shell 14 by painting, spraying or other standard method. The epoxy is of the self-curing type. The thickness of the layer may vary considerably depending upon the type of hull being formed. Since the epoxy is providing strength and rigidity as well as the bonding element it has been found that a thickness of approximately 0.040 inch is satisfactory.

After the layer of epoxy is applied to the shell 14, a die 20 presses the sheet 18 into the outer shell 14 thus forming the completed multilayer hull. As the epoxy cures at room temperature it will make a bond between the inner and outer aluminum shells. Since the epoxy layer when cured has inherent strength and rigidity it will provide the hull with a higher degree of rigidity than a single layer of aluminum of comparable thickness. Thus a hull is provided at much lower cost than that of a single layer aluminum hull. Nevertheless this multilayer hull will have the equivalent tear resistance strength of a non-layerized aluminum hull and even greater rigidity.

Another advantage lies in the ease with Which the inner and outer shells of the very thin aluminum can be formed. This speeds up production and lessens the cost of presses and dies.

If greater rigidity is desired several alternative structures can be incorporated in the hull. The outer shell may be formed with a downwardly extending keel 22 running substantially the length of the hull. Also at spaced positions, the' inner shell may be formed with upwardly projecting pedestals 24. These pedestals provide supports for the central portions of athwart seats 26 as well as stiftening the hull. The inner shell may further be formed with inwardly projecting shelves 28 which provide support for the ends of the athwart seats 26. The voids created by such keel, pedestals and shelves are filled with the epoxy which materially adds to the rigidity of the hull.

If necessary screws and occasional rivets may be used to secure the athwart seats and keep seams closed. This could also be accomplished by welding contacting edges of the aluminum shells.

In the embodiment shown in FIG. 4 the sheets are corrugated and then formed. The corrugations 30 in the outer shell running generally keelwise and the corrugations 32 in the inner shell running generally athwartship. When the spaces are filled with epoxy the unit will be extra rigid and strong.

I claim:

1. A multilayer hull for a small lightweight boat comprising:

an outer hull skin formed from a sheet of aluminum and provided with a downwardly formed longitudinally extending groove forming a keel;

an inner hull skin formed from a sheet of aluminum and designed to nest within the outer hull skin, said inner hull having upwardly projecting pedestals;

said sheets of aluminum having a thickness of from 0.010 to about 0.020; and

a layer of resinous self-curing epoxy between said skins,

said layer being approximately 0.040" thick except in the voids created by said groove and said pedestals so that said layer, in addition to bonding said skins, also has inherent strength and rigidity to provide the hull formed from thin sheets of aluminum with a degree of rigidity greater than a hull formed from a single layer of aluminum the thickness of which is at least as great as the total thickness of said multilayer hull.

References Cited UNITED STATES PATENTS Seely 114-80 Heslop 9 6 Hirota 114-69 Wagemaker 9-6 Shipley et al. 161--136X Swanson 9 6 Fuller 114-665 Weinheimer et al. 161-186X U.S. Cl. X.R. 

